The present invention relates generally to systems for obtaining ocular measurements, and particularly to an ultrasonic diagnostic scanner for measuring the axial length of an eye.
Ultrasonic vibrations or sound waves are frequently used in the field of medicine, for example, to determine information about certain internal characteristics of a person, organ or object. The ultrasonic vibrations are typically transmitted through a probe-type device which is placed in contact with a patient's body or other object, and the vibrations reflected back from internal components or organs are received by the probe. One such application involves ultrasonic diagnostic scanners for measuring the axial length of an eye from the cornea to the retina of the eye. These ultrasonic diagnostic scanners have typically measured the axial length of an eye by examining echo reflections which exceed a certain threshold level and recording or storing the time it takes for a certain number of these echo reflections to occur. This time value may then be related to a distance of length value through well known equations which correlate the time elapsed and the velocity at which the ultrasonic vibration was transmitted.
One or more of these distance equations are usually programmed into the ultrasonic diagnostic scanner so that the axial length measured may be conveniently displayed as a numerical value for the physician conducting the ocular examination. Some prior ultrasonic diagnostic scanners have also employed cathode ray tube video screens so that a real-time image of the echo reflections may be displayed. These ultrasonic diagnostic scanners have generally been classified as "A-Scans" which register only the amplitude of the echo reflections as they return, and "B-Scans" which provide for the brightness modulation or grey-scale variations necessary to produce a two-dimensional image of the eye from the echo reflections.
One example of a prior ultrasonic diagnostic scanner is the COMPU-SCAN (Trademark) Biometric Ruler, model U2020, manufactured by the Storz Instrument Company, the assignee of the present invention. This instrument includes a self-contained computer which performs the necessary lens calculations, and a cathode-ray tube for displaying an A-Scan of the echo reflections. An ultrasonic probe which is useful both for this instrument, as well as for the present invention is disclosed in U.S. patent application Ser. No. 436,845, Filed on Oct. 26, 1982, and entitled "Ultrasonic Probe", now abandoned. This patent application is also assigned to the assignee of the present invention, and is hereby incorporated by reference.
Another instrument useful in obtaining ocular measurements is the CORNEO-SCAN (Trademark) Ultrasonic Pachymeter, model CS1000, also manufactured by the Storz Instrument Company. This instrument is used to measure the thickness of the cornea of an eye, and includes a self-contained computer which performs the corneal thickness calculations, and a liquid crystal display (LCD) for displaying the numerical value of the corneal thickness. This instrument also includes circuitry for producing electronically synthesized speech, such as the word "ready" when the instrument is ready to make a measurement. The speech circuitry in this unit is also capable of reciting the standard deviation value for a number of measurements taken.
It is a principal objection of the present invention to provide an improved ultrasonic system for obtaining ocular measurements.
It is a more specific object of the present invention to provide an improved ultrasonic diagnostic scanner for measuring the axial length of an eye.
It is another object of the present invention to provide an ultrasonic diagnostic scanner capable of detecting an axial misalignment condition.
It is an additional object of the present invention to provide an ultrasonic diagnostic scanner capable of detecting a corneal depression condition.
It is a further object of the present invention to provide an ultrasonic diagnostic scanner capable of automatically adjusting its sensitivity.
It is yet another object of the present invention to provide an ultrasonic diagnostic scanner capable of automatically adjusting the threshold at which echo reflections are processed.
It is yet a further object of the present invention to provide an ultrasonic diagnostic scanner capable of displaying an echo histogram of the echo reflections on a liquid crystal display.
In accordance with the foregoing objects, the present invention provides an ultrasonic diagnostic scanner which generally comprises transmitter means for causing a transducer to transmit an ultrasonic signal, receiver means for receiving echo signals and for producing a peak signal at substantially the maximum amplitude of the echo signals when the echo signals exceed a predeterminable threshold level, programmable means for producing count signals indicative of the times between the transmission of the ultrasonic signal and the occurrence of a selected number of peak signals and between the occurrence of predetermined peak signals, microcomputer means for controlling the transmitter and programmable means, and output means for generating a perceptible output indicative of the ocular parameter being measured. The ultrasonic diagnostic scanner also includes sensitivity adjustment means for maintaining a predetermined amplitude level of at least one of the echo signals under the control of the microcomputer means. Threshold adjustment means is also provided for adjusting the predeterminable threshold level under the control of the microcomputer means. A dot matrix liquid crystal display is also included for visually displaying an echo histogram of the echo signals.
Additional advantages and features of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :